This disclosure relates to emergency backup devices and systems and in particular to emergency backup device for light-emitting diode (LED) loads.
Conventional direct current (DC) LED boards with external alternating current (AC) LED drivers are becoming increasingly less desirable for reliability and long term use, at least within some lighting applications. More recently, AC driver-on-board (DOB) LED modules with on-board electronics are becoming more popular as the LED light source of choice. AC DOB LED modules can be commercially available, such as those manufactured by Seoul Semiconductor, Luxtech, Lynk Labs, and III-N Technology with many Asian companies.
Unlike external LED drivers that use electrolytic capacitors and that may fail at, for example 20,000 hours, the AC DOB LED modules use solid states electronics that can last up much longer, for example 100,000 hours. The AC LED modules are compact and low profile in design, and can be used with dimmers and direct mains line voltage such as 120 vac, 220 vac, or 277 vac power, which can be readily available to power lighting in the United States and Canada, and around the world.
With power failures, rolling black-outs, brown-outs, over/under input voltage conditions, and unforeseen power outages, there becomes a need for inexpensive and affordable emergency backup power devices to work with these AC LED modules. These emergency backup devices need to be small, compact, and cost-effective to work with the new AC driver-on-board (DOB) LED light engines and AC LED modules used in luminaires to provide adequate emergency lighting for the safe egress of persons from a building, office, apartment, school, store, or other establishment quickly and efficiently.
Conventional backup power systems for AC devices include uninterruptible power supplies (or UPS). A uninterruptible power supply, also uninterruptible power source, UPS, or battery/flywheel backup is an electrical apparatus that provides emergency power to a load when the input power source, typically mains power, fails. The on-battery runtime of most uninterruptible power sources is relatively short at only a few minutes, but is sufficient to start a standby power source or to properly shutdown the protected equipment.
Inverter battery backup systems are also commonly used in emergency lighting today. Inverter systems are primarily designed for higher power applications to provide full power 120 vac to multiple fixtures. The drawback here besides the expensive cost of these systems is that they require larger and heavier batteries to operate and to provide the emergency backup capacity during a power failure condition.
Modern UPS systems may have three categories: on-line, line-interactive, and off-line standby. An on-line UPS system uses a “double-conversion” method of accepting AC input, rectifying to DC for passing through the rechargeable battery or battery strings, then inverting it back to 120 vac/230 vac for powering the protected equipment. A line-interactive UPS maintains the inverter in line and redirects the battery's DC current path from the normal charging mode to supplying current when the power is lost. In an off-line standby system, the load is powered directly by the input power and the backup power circuitry is only invoked when the utility power fails. Most UPS system below 1 kVA are of the line-interactive or of the off-line standby variety, which are usually less expensive.
For an off-line standby UPS, the typical protection time is 0-20 minutes of backup capacity, which is usually not expandable. In a line-interactive UPS, the typical protection time is 5-30 minutes of backup capacity. The line-interactive UPS can be expanded to several hours of backup capacity, but it will be very costly. Power from the present UPS is generally at full maximum output, so the load, such as LED load or AC LED module will be at full brightness and drawing the maximum amount of energy even during a blackout. It then becomes apparent that the main drawback for an inexpensive and affordable UPS system for use with AC LED modules is the limited backup time to power the light from the AC LED module during an emergency AC power failure condition.
The primary codes used to determine proper application of emergency lighting systems include: International Building Code (IBC), NFPA 101: Life Safety Code, NFPA 70: National Electrical Code, NFPA 110: Standard for Emergency and Standby Power Systems, NFPA 111: Standard on Stored Electrical Energy Emergency and Standby Power Systems, and NFPA 99: Health Care Facilities Code. Among these codes, OSHA 29CFR and NFPA 101 outline the basic requirements for emergency lighting as follows: (a) emergency lighting must last for at least 1.5 hours or 90 minutes after power failure; (b) emergency lighting must emit 1.0 foot-candles (10.8 lux) of light at any point in the building and 0.1 foot-candles of light along the emergency exit path at floor level; (c) after the emergency illumination period of at least 1.5 hours or 90 minutes, it is permissible for the illumination to fade to 0.6 foot-candles of light at any point in the building and 0.06 foot-candles of light along the emergency exit path at floor level.
The testing requirements for emergency backup lighting during a loss of AC power include function test and discharge test. Function test may require that: (a) all emergency luminaires should be tested by breaking the supply to them and checking that they operate satisfactorily; (b) the supply must then be restored and the charging indicator must be seen to be operating correctly; and (c) this test must be performed at least once per month and the results logged. Discharge test may require that: (a) the emergency luminaires must be tested for their full rated duration period and checked for satisfactory operation; the supply must then be restored and the charging indicators rechecked; (c) this test must be performed at least annually and the results logged. However, some existing systems may not be able to meet these requirements. Further, there also becomes a need for a small and compact package with sufficient battery backup power.
This document describes systems and methods that are intended to address at least some issues discussed above and/or other issues.